This invention relates to a majority decision method and a majority decision circuit for use in a receiver circuit to which an original frame is transmitted from a transmitter circuit through a channel susceptible to disturbances. Such a majority decision circuit is indispensable in, for example, an automobile digital communication network in which the original frame is repeatedly transmitted either five times or eleven times. The original frame comprises a plurality of original data or information bits.
More in general, the majority decision circuit receives the original frame an odd predetermined number of times as successively received frames, each comprising received data bits in correspondence to the respective original data bits and consequently to the received data bits of any one of others of the received frames, respectively, and is for determining a majority of the received data bits in each set, which received data bits are in correspondence to each other in the successively received frames. Such a majority is determined in order to provide a resultant frame comprising resultant data bits which are in correspondence to the respective original data bits and therefore to the received data bits of each received frame, respectively, and are best possible reproductions of the original data bits.
In the manner which will later be described more in detail, the majority is determined according to prior art after the successively received frames are all received. This has made it inevitable to use a great number of flip-flops and consequently an enormous number of transistors. The majority is referred to as an entire majority depending on the circumstances.
A conventional majority decision circuit comprises a plurality of buffers for memorizing the received data bits of the respective received frames. A logic operation unit is connected to the buffers and is used in successively determining the majority of the received data bits memorized in the buffers as a set of corresponding data bits of the respective received frames. The data bits in each received frame are, for example, eighty in number. When the received frames are five in number, the buffers must be composed of as many as four hundred flip-flops. Each flip-flop comprises from twenty to thirty transistors if implemented by an integrated circuit (IC). The conventional majority decision circuit has therefore had to comprise about ten thousand transistors.